Tag: Earth surface

[/caption]Most of the Earth surface, about 70%, is covered with water. The remaining 30% is made up of the seven continental landmasses. Underneath the water that fills the oceans, and the dirt and plants that cover the continents, the Earth’s surface layer is made of rock. This outer layer formed a hard, rocky crust as lava cooled about 4.5 billion years ago. This crust is broken into many large plates(tectonic plates) that move slowly relative to each other. The mountain ranges around the world formed when two plates collided and their edges are forced up. Many other surface features are the result of the movement of these tectonic plates. The plates move anywhere from 25 to 100 mm per year. About 250 million years ago most of the land was connected together.

The rocky layer under the soil of the Earth is called the crust. This comprises the continents and ocean basins. The crust has a variable thickness, being 35-70 km thick on the continents and 5-10 km thick in the ocean basins. The crust is composed mainly of alumino-silicates. The entire crust occupies just 1% of the Earth’s volume. The temperature of the crust increases as you go deeper into the Earth. It starts out cool, but can get up to 400 degrees C at the boundary between the crust and the mantle.

The tectonic plates are actually floating on the molten asthenosphere which is the lower mantle of the Earth. Earthquakes, volcanoes, mountains, and oceanic trench formation occur along plate boundaries. The plates are in constant motion. The reason that tectonic plates are able to move is the Earth’s lithosphere has a higher strength and lower density than the underlying asthenosphere. Their movement is dictated by heat dissipation from the Earth’s mantle. Lateral density variations in the mantle result in convection, which is transferred into plate motion through some combination of frictional drag, downward suction at the subduction zones, and variations in topography and density of the crust that result in differences in gravitational forces.

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Episode 660: Crew Dragon Reaches the Station. What it Took to Replace the Space Shuttle

On Sunday, May 31st, 2020, a SpaceX Crew Dragon capsule carrying astronauts Robert Behnken and Douglas Hurley docked with the International Space Station. This was a tremendous accomplishment for SpaceX and NASA, giving the United States the capability of launching its own astronauts, and no longer relying on its Russian partners.

This was the 5th time that US astronauts went into orbit on a new kind of space vehicle, following in the footsteps of Mercury, Gemini, Apollo, and the Space Shuttle.